My reasoning is:
A charter operator being in charge of and responsible for multiple lives other than their own. Size and type I guess could be argued about, but all vessels have potential issues on coastal bar crossings - small x wave size, large x lower draught-shallow bottom in parts. the current rules could certainly be looked at re epirbs and life jackets (type and when you have to wear them on coastal bar crossings)
Access during chaos, initial human nature is self preservation , ie need to get to the surface to breath before anything else.
the then current position of the epirb is then difficult in an up turned boat as all are already exhausted, some injured, 2 cant swim (1 due to back injury) and many in shock due to the circumstance, at this time near dangerous to attempt to get to the epirb / flares / life jackets. keep in mind, the waves don't just stop while you're sitting around waiting, the pounding by waves/wash continues to wash all survivors off of the partial safety of sitting on / clinging to the upturned hull, all helping each other and the injured and those who cant swim, so there is little recuperation time to 'go for a look and hope to not get hurt during the exercise'.
So back to the point, no one would have to set it off if it were hydrostatic, it would turn itself on when immersed under water.
This is just my opinion from my experience,